An innovative timber-steel hybrid beam consisting of glulam mechanically reinforced by means of steel rod: Analytical and preliminary numerical investigations

Abstract

There is an increasing interest in large-dimensional timber structural elements within the construction sector in order to fulfil the combined demand of sustainability, open spaces and architectural flexibility. Current timber technology allows for efficient production of long-size beams, but many problems are related to their overall high costs due to difficulties in transportation, manufacturing on site and handling during the mounting phase. Hence, the aim of this work is to propose and study an innovative timber-steel hybrid structural element composed of shorter pieces of beams connected and reinforced by means of a system consisting of steel shear keys and steel rods. The small timber elements and steel devices can be prefabricated with low costs and easily assembled into large elements at the construction sites. The proposed system can also be used for retrofitting of existing timber members when it is necessary to increase their strength, stiffness and ductility. The structural behavior of the proposed system was therefore studied both as a connection and as a retrofitting technique, which were analyzed via two types of hybrid beams, one with a splice at mid-span and one without, separately. A simple glulam beam with the same geometrical characteristics of the two hybrid structures was also investigated for the comparison of the structural behavior. The analytical results show that the hybrid beams with and without splice have both obtained significant increasement in the stiffness, strength and ductility. The numerical analyses are limited in the elastic stage due to the elastic mechanical properties assigned to the structural components. The numerical results show good agreement with the analytical ones for each type of beam in terms of the stiffness in the elastic stage. Finally, the influence of the parameters such as the distance between shear keys, slip modulus of shear keys and diameter of rod, on the structural behavior of hybrid beams is discussed in this paper. • An innovative system made of steel shear keys and rods to create long beams from smaller ones. • The system can be used as retrofitting technique to increase strength and stiffness of existing floors. • Considerations on ductile behavior of the proposed hybrid beams are illustrated. • Layout of hybrid beams improved through parametric studies with planar 2D numerical models.